The present invention relates to a failsafe system which is especially useful in skid control systems and the like.
In vehicle skid control systems it is especially important that defects in the wiring connecting components of the system be made known since such defects can potentially render the skid control system unknowingly inoperative. Heretofore failsafe circuits have been included in skid control systems for monitoring open wires, failure of wheel speed sensors, etc. In mass-produced vehicles produced by assembly-line techniques it is typical to have prefabricated wiring harnesses which can be quickly installed on the vehicle and easily connected to the electrical components via suitable plugs. Such wiring harnesses can be checked before installation on the vehicle to insure proper circuit continuity between terminals of the plugs which mate which complementary plugs on electrical components. However, in certain specialized or custom types of vehicles, such as custom-built trailers for example, pre-fabricated harnesses are usually not used for reasons of cost and therefore, wiring is typically performed on a custom basis with individual wires being routed on the vehicle between the various components. With this assembly procedure, proper continuity and connection of the wiring cannot usually be conveniently and economically determined.
The present invention is directed to a failsafe system which provides a warning signal to indicate a fault in the skid control system indicative of either improperly connected or faulty wiring, failure of one or more of the failsafe circuits, or loss of electrical power in the system. The invention is especially advantageous in custom-built multi-axle vehicles having skid control for each axle, although it will be appreciated that the invention is useful in other applications. One feature of the invention provides a failsafe circuit for each skid control module which is operatively associated with each individual axle. A more specific feature of the invention involves the connection of these failsafe circuits in cascading fashion with the failsafe circuits being arranged and constructed to propagate a signal through the cascaded chain of failsafe circuits so long as electrical power is being supplied in correct polarity to each of the skid control modules. If power is lost at any module, a warning signal is given. The invention also provides a warning signal in the event of a wiring fault due to improper connections at assembly or due to a subsequent wiring fault in a properly connected wiring. Furthermore, the invention exhibits a self-checking feature wherein a failure of any of the individual failsafe circuits also provides a warning signal.
The foregoing features of the invention along with additional advantages and benefits thereof will be seen in the ensuing description and claims which are to be taken in conjunction with the accompanying drawing.